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December 7, 2011

Type 2 Diabetes Increased With Shift Work And Irregular Schedules

by editor

A new study published in the journal PLoS Medicine highlights the increased risk of type 2 diabetes for women who juggle irregular work and sleep cycles and the increasing risk entailed the longer that schedule is maintained.

The risk of developing type 2 diabetes increases steadily increases among female nurses with the years of shift work she puts in, the study found.

The study, led by Frank Hu, M.D., a professor of nutrition and epidemiology at the Harvard School of Public Health in Boston, analyzed data on 177,184 women between the ages of 42 and 67 who were followed for about two decades as part of the long-running Nurse´s Health Study.

The women were considered rotating night-shift workers if they worked at least three nights per month, with the addition of day and evening hours. Compared to nurses who worked days only, those who worked periodic night shifts for as little as three years were 20 percent more likely to develop type 2 diabetes. Those who clocked at least 20 years of shift work were nearly 60 percent more likely to develop the disease.

“The increased risk is not huge, but it´s substantial and can have important public health implications given that almost one-fifth of the workforce is on some kind of rotating night shift,” says Hu.

Irregular work hours disrupt the circadian rhythms, or “body clock”, which play a critical role in maintaining healthy blood-sugar metabolism and energy balance. Sleep deprivation and irregular sleep-wake cycles can lead to insulin resistance and rising blood-sugar levels, both harbingers of diabetes.

Much of the increase in diabetes risk can be explained by weight gain, which is exacerbated by shift work with its disruptions in eating and sleeping schedules making following a healthy lifestyle a challenge. But other, more subtle disturbances may also play a role.

“The overall risk associated with rotating shift work is probably due to the combination of biological factors resulting from disruption of circadian rhythms and... behavioral risk factors,” Hu says.

Amanda Gardner of CNN Health reports that the study was the largest to date to explore the link between shift work and diabetes, but the authors stress that more research will be needed to confirm the results, especially in other populations. The study included only female nurses and the vast majority were white, so the findings don´t necessarily apply to men or other ethnic groups, they say.

In an accompanying Perspective article, Mika KivimÃ¤ki from University College London, David Batty from the University of Edinburgh, and Christer Hublin from the Finnish Institute of Occupational Health in Helsinki, Finland (uninvolved in the research study) say, “We are increasingly residing in a ℠24/7´ society, thus the option to eradicate shift working is not realistic.”

“If the observed association between rotating shift work and [type 2 diabetes] is causal, as it may be, additional efforts to prevent [type 2 diabetes] among shift workers through promotion of healthy life styles, weight control and early identification and treatment of pre-diabetic and diabetic employees are needed.”

According to the US Centers for Disease Control and Prevention (CDC), approximately 15 million Americans work full time on evening shifts, night shifts, rotating shifts, or other irregular schedules.